Pulverizing bowl mill utlizing a segmented bull ring



June 23, 1964 BOGOT ETAL 3,138,337

PULVERIZING BOWL MILL UTILIZING A SEGMENTED BULL RING Filed March 26, 1963 2 Sheets-Sheet 1 E 46 12 lo FIG. I

INVENTOR ALEXANDER BOGOT BY LORENZ J. ANDRESEN THOMAS B. HAMILTON June 23, 1964 A. BOGOT ETAL 3,138,337

PULVERIZING BOWL MILL UTILIZING A SEGMENTED BULL RING Filed March 26, 1963 2 Sheets-Sheet 2 INVENTORS; ALEXANDER BOGOT LOR J. ANDRESEN THO B. HAMILTON BY Z ATTORNEY United States Patent 3,138,337 PULVERIZING BOWL MILL UTLIZING A SEGMENTED BULL RING Alexander Bogot, West Hartford, Conn., and Lorenz J.

Andresen, Chicago, and Thomas B. Hamilton, Arlington Heights, Ill., assignors to Combustion Engineering,

1516., Windsor, Comm, a corporation of Delaware Filed Mar. 26, 1963, Ser. No. 268,073 1 Claim. (Cl. 241103) This invention relates to apparatus for pulverizing material, and in particular to an improved ring which coacts with the rollers or grinding elements to perform the grinding action.

Many pulverizing mills today utilize a rotating bowl or table having a race or grinding ring upon which a number of rollers or balls rotate, to thus pulverize coal or other material it is desired to grind to a given fineness. It has been found that considerable wear in these pulverizing mills occurs on the grinding ring or race, and these rings must be periodically replaced. Because of the size of these rings, which are of one-piece forged or cast construction, a substantial portion of the mill must be dismantled in order to permit the worn ring to be removed and replaced. This results in excessive maintenance costs, and periodic and lengthy shutdown periods.

It is an object of our invention to provide a grinding ring for a pulverizing mill constructed in such a manner that it will have a long life, and will be easily and quickly replaceable when it does become worn.

Other objects and advantages will become apparent from the following description of an illustrative embodiment of our invention when considered with the accompanying drawings, wherein:

FIG. 1 is a cross-sectional side view of a bowl mill embodying our invention;

FIG. 2 is an enlarged plan view of the segmented bull ring;

FIG. 3 is a cross-sectional side view of the bull ring taken on line 33 of FIG. 2;

FIG. 4 is an enlarged plan view of one of the segments or members that make up the bull ring; and

FIG. 5 is a cross-sectional view taken on line 5-5 of FIG. 4.

Looking now to FIG. 1, numeral designates a bowl mill for grinding coal or other material therein. Inside the housing is positioned a rotatable bowl or table 12, mounted on shaft 14. Shaft 14 along with attached bowl 12 is rotated by means of worm wheel 18, which engages worm 16 mounted on motor driven shaft 20.

One or more grinding elements or rollers 22 are rotatably mounted on shafts 24. Adjustable spring 26 urges roller 22 towards the inner surface of the grinding ring.

Coal to be pulverized is introduced into the mill through inlet 28. Air enters through opening 30, and flows through annular space 31 to convey the ground material passing over the lip upwardly through the mill interior and into the classifier 34. The air and coal enter the classifier by way of inlets 32. The larger particles of unground coal fall back onto the grinding surface through bottom opening 36 for further grinding, and the finer particles carried along by the air are discharged through outlets 38.

Segmented bull ring 40 forms the grinding surface which coacts with the rollers 22 to perform the grinding action. The hub cone 42, having radial vanes 44 thereon, continuously throws the coal discharged through opening 36 back onto the grinding surface for further grinding. Screws 46 secure cone 42 to the bowl 12.

Covered opening 48 is provided in the bowl mill housing in order to permit access to the housing interior for maintenance and inspection purposes. Through this open- 3,138,331 Patented June 23, 1964 bull or grinding ring 40 when they become unduly worn. Looking now to FIGS. 2 and 3, the segmented bull or grinding ring is shown in more detail. A plurality of truncated wedge-shaped members 70 secured in side-byside relationship make up the annular grinding ring which is rotatable with respect to the rollers. An inner retainer ring 52, pressed downwardly against groove 50 in the inner peripheral surface of each segment, secures the inner surfaces of the members to the bowl 12. The retainer ring 52, which may be segmented, or made of three or more parts for ease of assembly, is pressed firmly against groove 50 by the bowl hub cone 42, which is fastened to the bowl 12 by screws 46.

The segments 70are cast, and none of the surfaces thereon are thereafter machined. Thus there maybe some slight irregularities on the surfaces thereof. It is for this reason that the retainer ring 52 is needed. With-' out the ring, if there were high spots on the inner peripheral surface of some of the segments, these segments would be the only ones contacted by the bowl hub cone. The retainer ring 52 is made of a soft iron, or other suitable material which will be crushed out of shape by the bowl hub cone when screws 46 are tightened. In this manner the inner edge of each of the segments will be securely fastened to the bowl.

The outer peripheral surfaces of the segments 70 are secured to the bowl 12 by outer retainer ring 56, which is pressed down upon groove 54 by a plurality of screws 58, threaded through the peripheral portion of bowl 12. Again, retainer ring 56 is made of three parts for ease of assembly. Bowl extension ring 64 fits on the inner annular edge of bowl 12 and serves the purpose of retaining the coal to be pulverized within the grinding bowl.

As best seen in FIGS. 4 and 5, each segment 70 contains a recess 60 in the lower surface thereof and a rib 62 extending up out of the plane of the upper surface. The purpose of these features will be explained later.

Previous to this invention, the bull or grinding rings had been of one-piece forged or cast construction. The materials that could be used for making these rings were limited in number, due to the fact that these rings would necessarily have to be machined and worked prior to their installation in the bowl mill. The truncated wedgeshaped members 70 of the present invention are cast, and need not be machined or worked at all. Thus it is possible to make these members of a very hard material having extremely good abrasive resistant characteristics. The metal used can have a hardness on the order of Rockwell hardness No. 75. A typical material that can be used is Nihard or Diamite.

The recess 60 covers an area substantially larger than the area which is not recessed in the bottom of each member 70. This reduces the weight of each member, and is also a saving of material. The recess also permits only the outer peripheral edge of the bottom surface to rest against the bowl 12. Thus if there are some slight irregularities in the surface, the element will fit better than would be the case if the recess were not present. Since these elements are made of a material not capable of low cost machining, this feature is significant.

The ribs 62, which extend up out of the plane of the upper surface, and run along adjacent one of the side surfaces from the inner peripheral surface to the outer peripheral surface, serves a two-fold function. Without these ribs, the surface of the bowl ring tends to become shiny and polished, with the result that the material being pulverized and hence the rollers tend to slip somewhat thereon. These ribs prevent slippage of the material and rollers. The ribs, by being positioned adjacent to one of the flat side surfaces, also prevents the segments from becoming unduly worn along their adjoining edges, by

preventing the rollers from coming into direct contact with these joints.

While we have illustrated and described the preferred embodiment of our invention, it is to be understood that such is merely illustrative and not restrictive and that variations and modifications may be made therein without departing from the spirit and scope of the invention. We therefore do not wish to be limited to the precise details set forth but desire to avail ourselves of such changes as fall within the purview of our invention.

What we claim is:

In a grinding mill, a bowl, means for rotating said bowl, a segmented ring secured to the bowl, a grinding roll positioned in a manner to coact with the segmented ring to accomplish grinding, said segmented ring being made up of a plurality of one piece cast construction truncated wedge-shaped members which, when secured together in side-by-side relationship form an annular ring, each truncated wedge-shaped member having two fiat side surfaces adapted to abut against the flat side surfaces of the next adjacent members, a lower surface which lies against the bowl, an upper surface which coacts with the grinding roll, an inner peripheral surface, an outer peripheral surface, a rib extending up out of the plane of the upper surface, said rib extending from the inner peripheral surface to the outer peripheral surface adjacent one of the flat side surfaces, the upper surface being flat with the exception of the rib, a groove formed in both the inner and outer peripheral surfaces extending from one side surface to the other side surface, retaining rings positioned Within the grooves of both the inner and outer peripheral surfaces, each retaining ring being made up of several separable portions, each portion of each retaining ring encompassing a plurality of the wedge-shaped members, means for firmly clamping all of the wedge-shaped members between the retaining rings and the bowl, at least one of said retaining rings being made of a malleable metal so that it will conform to any irregularities on the surfaces of the grooves in the wedge-shaped members.

References Cited in the file of this patent UNITED STATES PATENTS 1,110,222 Morat Sept. 8, 1914 1,400,123 Wolff Dec. 13, 1921 2,848,170 Crites Aug. 19, 1958 3,065,920 Johnson et a1 Nov. 27, 1962 

